1. Field of the Invention Group
The present invention relates to a method for controlling communication paths and a communication control system in a communication network.
A communication network has been becoming more complex and larger in scale as they adapt to handle various configurations of transmission modes and different transmission speeds. In such a communication network, it is necessary to manage the overall operational states of the communication paths in order to facilitate the control for formation and release of communication paths.
2. Description of the Related Art
As mentioned above, a communication network is generally constituted to handle a mixture of modes and speeds. Various transmission modes, for example, the plesiochronous digital hierarchy (PDH), synchronous digital hierarchy (SDH), and asynchronous transfer mode (ATM) are used and various transmission speeds are operated at.
As will be explained in detail later by referring to the drawings, such a communication network is generally managed for the different transmission modes or transmission speeds. For example, the communication paths having a transmission speed of 2 Mbps are managed by first and second sub-network management systems, while communication paths of a transmission speed of 52 Mbps are managed by a third sub-network management system. The overall communications network is managed by a main network management system which functions as a higher level system of these sub-network management systems.
Management of such complex communications networks tends to arrange these communication paths hierarchically as seen for example in Recommendations G.805 of the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T).
In such a communication network, if communication paths are arranged hierarchically, they are hierarchically constituted by, e.g., first SDH communication paths (VC3-TU3)(VC: Virtual Container, TU: Tributary Unit) of 52 Mbps, second SDH communication paths (VC12-TU12) of 2 Mbps, and third PDH communication paths of 2 Mbps. These communication paths have respective cross connects. Namely, a third PDH communication path of 2 Mbps is constituted by part of a first communication path and part of a, second communication path.
Accordingly, when switching a cross connect of a first communication path from an unlocked state (in operational service) to a locked state, even if the cross connect of the second communication path forming part of the first communication path is supposed to be in the unlocked state, the second communication path is changed from the unlocked state to the locked state. Accordingly, also the third communication path forming part of the second communication path switches from the unlocked state to the locked state. In this way, higher level parts of the hierarchical structure influence the lower level parts. It therefore becomes possible to identify the state of a lower level by examining the state of the higher level.
When the cross connect of the third communication path is placed in the unlocked state from the locked state by setting of a path, it is necessary to confirm whether both of the first and second communication paths of the higher levels are in the unlocked state. Namely, when switching a lower level from the locked state to the unlocked state (in operational service) but if a higher level is not in the unlocked state, the communication path of the lower level will not enter operational service. Accordingly, as the number of hierarchies becomes larger, processing for deciding the state for every level has to be repeated and there arises a problem of a longer processing time.